On Friday, September 23, 2011 3:52:54 pm Timothy Garnett wrote: > Hi all, > > I was wondering if there was some good documentation on what kinds of > schema modifications block reads vs. which ones don't. For ex. we > recently had an issue where someone ran as part of a migration > > ALTER TABLE tname ALTER COLUMN cname SET NOT NULL; > > on a large table that is not inserted to or updated. While we'd expect > such an operation to block inserts/updates (writes) to the table, we were > surprised to observe that it also blocked selects (reads) from the table > as well, which we would not have naively expected (and caused a great deal > of headache). On the other hand creating an index on a table blocks > writes, but still allows reads (even a unique index), as documented in the > create index docs. Is there a list somewhere of what operations block > selects (reads) to a table that we should watch out for? http://www.postgresql.org/docs/9.1/interactive/explicit-locking.html > > We are currently using PostgreSQL 9.0.3. > > Thanks! > Tim -- Adrian Klaver adrian.klaver@xxxxxxxxx -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
